Field of the Invention
The present invention relates to automated or remotely controlled methods and apparatus for cleaning soiled objective lenses on wide angle or “fish-eye” video cameras or sensors when mounted in a configuration that is exposed to dirty environments.
Discussion of the Prior Art
External view (e.g., front bumper, side-view, rear-view or back-up) cameras have been added to recreational vehicles and automobiles to enhance the driver's vision and to improve safety. Increasingly, a wide range of cars and SUVs include integrated video cameras which generate an image for display to the driver, operator or other occupants or users within the vehicle's interior.
Drivers often find it difficult to move their vehicles from parked positions when they cannot see or know what is behind the vehicle. The recent introductions of front-bumper, side-view and rear-view cameras in cars and SUVs by vehicle manufacturers allow drivers to see whether obstacles surround their vehicle using a display screen mounted either on a rear view mirror or in a navigation system screen.
The external image sensors such as those known as back-up or rear view cameras are typically mounted unobtrusively, and incorporated into existing features such as the vehicle's rear name plate. These external cameras are exposed to the vehicle's harsh environmental surroundings and are often soiled by mud, salt spray or dirt which accumulates on the lens. Accumulating dirt and debris often distort the image drivers are viewing, thus creating confusion, dissatisfaction or a safety issue due to poor judgment by relying on an unclear picture.
The advent of low cost, reliable imaging devices using solid-state sensor technologies (e.g., CMOS pixel sensor technology), combined with an improved cost/performance ratio for video displays capable of meeting automotive specifications, and an increasing application rate of video monitor displays for automotive navigation systems and the like, has lead to an increasing use of cameras or imaging sensors designed to give the driver a view of those areas around the vehicle which are not in the normal direct field of view of the driver, typically referred to as “blind spots”. These areas include the region close to the front of the vehicle, typically obscured by the forward structure of the vehicle, the region along the passenger side of the vehicle, the region along the driver's side of the vehicle rearward of the driver, and the area or region immediately rearward of the vehicle which cannot be seen directly or indirectly through the rear view mirror system. The camera or imaging sensor may capture an image of the rearward (or sideward or other blind spot area) field of view, and the image may be displayed to the driver of the vehicle to assist the driver in backing up or reversing or otherwise driving or maneuvering the vehicle.
The use of electronic cameras in vehicle imaging systems can significantly increase a diligent driver's knowledge of the space immediately surrounding the vehicle prior to and during low speed maneuvers, and thus contributes to the safe completion of such maneuvers. It is thus known to provide a camera or imaging sensor on a vehicle for providing an image of an exterior scene for the driver. Such a camera may be positioned within a protective housing, which may be closed about the camera or sensor and secured together via fasteners or screws or the like. For example, a metallic protective housing may be provided, such as a die cast housing of aluminum or zinc or the like. In particular, for camera sensors mounted on the exterior of a vehicle, protection against environmental effects, such as rain, snow, road splash and/or the like, and physical protection, such as against road debris, dirt, dust, and/or the like, is important. Thus, for example, in known exterior camera sensor mounts, a butyl seal, such as a hot dispensed butyl seal, or an O-ring or other sealing member or material or the like, has been provided between the parts of the housing to assist in sealing the housing to prevent water or other contaminants from entering the housing and damaging the camera or sensor positioned therein. However, such housings typically do not provide a substantially water tight seal, and water droplets thus may enter the housing. Furthermore, any excessive vibration of the camera sensor, due to its placement (such as at the exterior of the vehicle), may lead to an undesirable instability of the image displayed to the driver of the vehicle. Also, such cameras or sensors are costly to manufacture and to implement on the vehicles.
Such vehicle vision systems often position a camera or imaging sensor at an exterior portion of a vehicle to capture an image of an exterior scene. The cameras, particularly the cameras for rearward vision systems, are thus typically placed or mounted in a location that tends to get a high dirt buildup on the camera and/or lens of the camera, with no easy way of cleaning the camera and/or lens. In order to reduce the dirt or moisture buildup on the lenses of such cameras, prior art developers proposed using hydrophilic or hydrophobic coatings on the lenses. However, the use of such a hydrophilic or hydrophobic coating on the lens is not typically effective due to the lack of air flow across the lens, especially within a sealed housing. It has also been proposed to use heating devices or elements to reduce moisture on the lenses, within the sealed housing. However, the use of a heated lens in such applications, while reducing condensation and misting on the lens, may promote the forming of a film on the lens due to contamination that may be present in the moisture or water. Also, the appearance of such cameras on the rearward portion of vehicles is often a problem for styling of the vehicle. See, for example, prior art U.S. Pat. No. 7,965,336 to Bingle, et al. which discloses a camera module with a plastic housing that houses an image sensor, which is operable to capture images of a scene occurring exteriorly of the vehicle. Bingle's camera housing assembly is welded together with the image sensor and associated components within enclosed the plastic housing, and includes a “breathable” ventilation portion that is at least partially permeable to water vapor to allow emission of internal water vapor substantially precluding passage of water droplets and other contaminants, and so Bingle's design seeks to minimize problems arising from fluid impacting or accumulating within the housing.
Bingle also seeks to use coated lenses to keep the objective lenses' view clear, and Bingle's housing or cover 22 is optionally be coated with an anti-wetting property such as via a hydrophobic coating (or stack of coatings), such as is disclosed in U.S. Pat. No. 5,724,187. Bingle notes that a hydrophobic property on the outermost surface of the cover can be achieved by a variety of means, such as by use of organic and inorganic coatings or by utilizing diamond-like carbon coatings. But Bingle and others do not propose actually taking any affirmative action to remove road debris (e.g., accumulated dirt, dust, mud, road salt or other built-up debris) apart from using such coatings or surface treatments.
Based on consumer preference and at least a perceived improved ability to extract information from the image, it is desired to present an image to the driver that is representative of the exterior scene as perceived by normal human vision. It is also desirable that a vehicle's imaging devices or systems be useful in all conditions, and particularly in all weather and lighting conditions. However, it is often difficult to provide an imaging sensor which is capable of providing a clear image in poor weather, especially while driving. This is because conventional imaging systems typically have difficulty resolving scene information when the camera's objective lens is partially obstructed by accumulated debris (e.g., accumulated dirt, dust, mud, road salt or other built-up debris).
In order to have effective use of the camera-based visibility systems in all weather conditions, it is desirable to have an effective method of keeping the camera lens (or the housing surface protecting the objective lens) clean, but the potentially deleterious effects of moisture noted in Bingle remain. When driving or operating a vehicle during bad weather, drivers are especially reluctant to exit the vehicle to find and inspect the camera's lens.
This reluctance likely explains why the inventors of U.S. Pat. No. 6,834,904 (to Vaitus et al) included a “Nozzle” 92 “in close proximity to” lens 84 for the vehicle's camera or vision unit 71. The Vaitus '904 patent generally discloses the structure and method for mounting a “Vehicle Liftgate with Component Module Applique” wherein applique module 50 is adapted for attachment to vehicle liftgate 20 and, as shown in Vaitus' FIG. 2, module 50 includes a nozzle 92 which receives fluid from conduit 94, but, as noted in the description at Col 5, lines 5-25, “cleaning of lens 84 may be implemented in other ways” such as hydrophobic lens coatings. It appears that the module and nozzle arrangement described so indifferently in the Vaitus '904 patent was not deemed to be a practicable or effective solution meriting further development, and so appears to have been ignored.
Increasingly on modern vehicles, cameras or other sensors such as infrared image sensors are incorporated to provide additional information to the driver. Many of these sensing devices can become soiled and obstructed by dirt and debris common in the driving environment, eventually causing deterioration in the efficacy of the sensing device or possibly rendering it unusable, or providing an undesirable appearance. It is therefore desirable to periodically wash these sensing devices to reduce or eliminate the buildup of these obstructions. However, there are restrictions which are unique to certain sensor wash applications which limit use of traditional washer nozzles. Sensors may be located on or near the vehicle centerline, in close proximity to branding badges or other cosmetically important features on the vehicle, and it is undesirable to add a visible washer nozzle in this aesthetically important area. Another restriction is that sensors may have very wide fields of view, up to or exceeding 180°, so that a traditional lens washer nozzle configuration would have to be within the sensor's field of view in order to be able to direct fluid onto the sensor surface at an angle which would provide acceptable cleaning.
Being located within the sensor's field of view may block a significant portion of area the sensor would otherwise be capable of monitoring. A third constraint which affects sensor wash applications is that the sensor may frequently be located on an area of the vehicle which sees higher levels of contamination than do typical washer nozzle mounting locations, such as on the front grill or the rear lift gate. Washer nozzles in these locations may be at a higher risk of being clogged by the same material which is obscuring the sensor. There is a need, therefore, for a convenient, effective and unobtrusive system and method for cleaning an exterior objective lens or wide-angle sensor's exterior surface, and preferably by remote control.